Hydraulic feed systems



7 D. J. K. STUART EfAL 3,353,429

HYDRAULIC FEED SYSTEMS Filed July 12, 1965 v 2 Sheets- Sheet 1 1967 D. J. K. STUART ETYAL 3,353,429

, HYDRAULIC FEED SYSTEMS Filed July 12, 1965 2 Sheets-Sheet 2 United States Patent 3,353,429 HYDRAULIC FEED SYSTEMS Duncan James Keith Stuart and Brian Queenborough,

Solihull, England, assignors to Edward Williams Holdings Limited, Birmingham, England, a British company Filed July 12, 1965, Ser. No. 471,220 Claims priority, application Great Britain, July 25, 1964-, 26,279/ 64 7 Claims. (Cl. 82-21) ABSTRACT OF THE DISCLOSURE A hydraulic feed system including a pair of pistons and cylinders so arranged that as the pistons are moved together, the liquid volume increases in one cylinder and decreases in the other; a pair of feed conduits carrying liquid to and from the cylinders; and valve means interconnecting the cylinders and the conduits and which means can be operated to change the movement speed of the pistons without changing the liquid flow speed in one of the conduits.

This invention relates to hydraulic fed systems particularly for use in machine tools for traversing various parts thereof.

According to the invention an hydraulic feed system includes a pair of cylinders, a pair of pistons slidable in the cylinders respectively and interconnected externally of the cylinders, the pistons and cylinders being so arranged that as the pistons are moved together the volume of liquid in one cylinder is increased and the volume of liquid in the other cylinder is decreased, a pair of feed conduits for carrying liquid to and from the cylinders and valve means which so interconnect the cylinders with said conduits that the valve means can be operated to change the speed of movement of the pistons without changing the speed of liquid flow in one of said conduits.

Reference will now be made to the accompanying drawings in which FIGURE 1 is a diagrammatic plan view illustrating the manner in which two examples of the invention are applied to an automatic lathe and FIGURE 2 is an hydraulic circuit diagram of the arrangement shown in FIGURE 1.

Referring to FIGURE 1, in the lathe shown there is a bed 10 carrying a turret rest which can be adjusted along the bed and affixed thereto.

On the turret rest a turret slide saddle 11 is slidable. Mounted on this slide 11 is an indexable turret 12 aligned with the headstock spindle 13. The turret slide 11 is movable along the bed 10 by means of a pair of hydraulic cylinder units 14, 15, secured to the turret rest and having piston rods 16, 17, attached to an end member 18 of the slide 11.

There is also provided an intermediate saddle 19 which can be adjusted along the bed 10 and locked in position. This saddle 19 is provided with a cross-slide 20 mounted for motion in a direction perpendicular to bed 10. Movement of the cross-slide 20 is effected by means of a pair of hydraulic cylinder units 21, 22 secured to saddle 19 and having piston rods 23, 24 attached to cross-slide 20.

Turning now to FIGURE 2 it will be observed that the cylinders 25, 26- of units 14, are of equal bore and the piston rods 16, 17 are of equal diameter. Furthermore, the two cylinders 25, 26 are parallel and the rods 16, 17 project in the same direction. Cylinder unit 14 has, however, a dummy piston rod 27 of greater cross sectional area than rod 16 projecting from the opposite end of its cylinder 25. Cylinder 25 has a port 28 at the end from which the dummy piston rod 27 projects and a Patented Nov. 21, 1967 port 29 at the other end. The ends of cylinder 26 have ports 30, 31, of which port 31 is at the end from which piston rod 17 projects.

Pressurised liquid for cylinder units 14 and 15 is supplied via a pipeline 32 and liquid expelled from three units is led to drain via speed control devices 33. Speed control may be effected through the intermediary of a plurality of flow restriction which can be selected by the operation of suitable valve gear. Line 32 and devices 33 are connected respectively to two ports 35, 36 of a reversing valve 34. The other two ports 37, 38 of this valve are arranged so that with the valve in one position ports 35 and 37 intercommunicate as do ports 36 and 38. In the other position port 36 communicates with port 37 and port 35 communicates with port 38.

Port 37 is connected via feed conduit 37:: to port 30 of cylinder unit 15 and port 38 is connected via feed conduit 38a to port 29 of cylinder unit 14. Port 28 of unit 14 is connected to port 40 of a three-Way valve 39. Valve 39 also has ports 41, 42 connected respectively to conduits 37a and 38a and arranged so that in one position of valve 39 port 41} is connected to port 41 and in the other position to port 42. Port 31 of unit 15 is connected to port 44 of a similar three way valve 43 which also has ports 45, 46 connected respectively to conduits 37a and 36a.

The circuits associated with cylinder units 21 and 22 are in principle similar to those described above. In this instance, however, cylinder unit 21 is of larger bore than unit 22, the latter being single acting. The piston rods 23, 24 project in the same direction as before. Cylinder unit 21 has ports 47, 48 at opposite ends the former being at the end from which rod 23 projects. Unit 22 being single acting, has a single port 49 at the end from which rod 24 projects.

Ports 48, 49 are connected via conduits 51a, 52a respectively to ports 51, 52 of reversing valve 50 like valve 34. Valve 50 also has ports 53 and 54 connected to a supply line 55 and through speed control devices 56 to drain respectively. Port 4'7 is connected to port 58 of a three way valve 57 which also has ports 59, 61) connected respectively to conduits 51a, 52a.

The supply of liquid to line 55 is taken from a first pump 61 at a pressure determined by pressure regulating valve 62 and under the control of valves 63, 64. The supply line 32 is taken from a second pump 65 at a pressure determined by regulator 66 and under the control of valve 67. Line 32 can also receive liquid from pump 61 via valves 63 and 70 in series. Valve 63 is a three way valve which connects pump 61 either to line 55 or to valve 70. Valve 64 is a stop valve which when opened connects line 55 to drain. Valve 67 is a three way valve for connecting line 32 either to pump 65 or to drain, whilst valve 70 is a three way valve which connects the line from valve 63 either to line 32 or to drain.

All the valves mentioned herein are pneumatically operated under the control of an automatic programming system.

In the condition shown both lines 32 and 55 are connected to drain. For normal operation of the turret slide 11, therefore, valve 67 is operated to connect line 32 to pump 65. Line 32 thus becomes connected to port 29 of unit 14 and to port 31 of unit 15. Since ports 28 and 30 are connected through devices 33 to drain, the slide 11 is moved to the left in FIGURE 1. The rate at which liquid is expelled is limited by the selection of devices 33 and known means are provided to ensure that this rate is constant for a given selection and independent of the load resisting sliding motion of slide 11.

If valves 39 and 43 are now operated line 32 will become connected to ports 28 and 29 of unit 14 whereas both ports 30 and 31 of unit 15 will be connected to devices 33. Since the dummy piston rod 27 is of larger cross O sectional area than red 16-there is a net force on the piston of unit 14 to displace it to the left, Liquid from port 28 enters port 29 with liquid from the pump. In the case of unit 15 some of the liquid displaced from port 30 is drawn into port 31 so that the amount of liquid displaced into devices 33 for a given movement of the slide 11 is considerably lower than when ports 28 and 30 alone were connected to devices 33. Since the rate of flow through devices 33 is kept constant for a selected setting it will be appreciated that changing over valves 39, 43 as described results in a considerable increase in the speed of motion of the slide 11.

Operation of reversing valve 34- results in the slide 11 being moved to the right. The arrangement of the controls 33 will preferably be such that a range of speeds are available which range is supplemented by coarse/ fine variation available by operation of valves 39, 43.

Under some circumstances-for example when the slide 11 is completing a stroke to the right and it is desired to use the saddle motion to index the turret 12 it may be found that insufiicient force is available in a coarse feed rate, whereas the indexing would be too slow and therefore waste time, at a fine feed rate. It will be appreciated, however, that if valves 34 and 39 are changed over from the position shown whilst valve 43 is left unchanged, ports 28, 29 and 31 will be connected through devices 33 to drain whilst port 30 is connected to pump 65. Under these conditions the amount of liquid required to move the slide 11 at the desired high speed is obtained by operating valve 70, thus augmenting the supply with liquid from pump 61. Similarly rapid cutting feeds faster than the normal range of fine feeds can be obtained.

When it is desired to move the cross slide valves 63 and 64 are operated. In the condition shown pressurised liquid is supplied to port 48 only, ports 47 and 49 being connected to drain via the devices 56. The cross-slide 20 is, therefore slid downwardly as seen in FIGURE 1. If now valve 57 is operated port 47 will also be connected to line 55. Since both sides of the piston of unit 21 will be subject to high pressure the presence of piston rod 23 on one side will cause the cross slide 20 to be moved downward with liquid spilling from port 47 into port 48. The only liquid passing through devices 56 will be that expelled from port 49 so that, once again, a coarser rate of feed is established.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. An hydraulic feed system including a pair of cylinders, a pair of pistons slidable in the cylinders respectively and interconnected externally of the cylinders, the pistons and cylinders being so arranged that as the pistons are moved together the volume of liquid in one cylinder is increased and the volume of liquid in the other cylinder is decreased, a pair of feed conduits for carrying liquid to and from the cylinders and valve means which so interconnect the cylinders with said conduits that the valve means can be operated to change the speed of movement of the pistons without changing the speed of liquid flow in one of said conduits.

2. An hydraulic feed system as claimed in claim 1 in which the two cylinders are parallel and have interconnected piston rods projecting in the same direction therefrom.

3. An hydraulic feed system as claimed in claim 2 in which one of the piston and cylinder units is single acting and has a single port at the end at which its piston rod projects, said port and a port at the opposite of the other cylinder being connected to said conduits respectively and said valve means comprising a valve adapted to connect a port at the end of said other cylinder from which the piston rod projects to either conduit.

4. An hydraulic feed system as claimed in claim 2 in which one cylinder has a dummy piston rod projecting from the end thereof opposite the end from which the piston rod proper projects and in which each cylinder has ports at both ends, the ports at the end of said one cylinder at which the piston .rod proper projects and at the opposite end of the other cylinder being connected to the two conduits respectively and the other two ports being connected respectively to a pair of valves whereby each of said other two ports can be connected to either of said conduits.

5. An automatic lathe of the type described including a bed, an adjustable turret rest on the bed, a turret slide movable along the bed and an hydraulic feed system for moving the turret slide along the bed, said hydraulic feed system comprising first and second parallel identical cylinders attached to the turret rest, first and second pistons slidable in said cylinders respectively, first and second piston rods projecting in the same direction from the cylinders respectively and attached to the turret slide, a dummy piston rod on said first piston of cross-sectional area greater than that of the first piston rod and projecting from that end of the first cylinder which is remote from the end thereof from which said first piston rod projects, a source of pressurised fluid, a reservoir, selectively operable speed control devices controlling the flow of fluid to the reservoir, first and second conduits connectible to the source and to said speed control devices, said first conduit being a first valve for connecting the first conduit to the end of the first cylinder from which the dummy piston rod projects When said first Valve is in a first condition and for connecting said second conduit to the end of the first cylinder from which the dummy piston rod projects when the first valve is in a second condition, said second conduit being permanently connected to the end of the first cylinder from which the first piston rod projects, and a second valve for connecting the second conduit to the end of the second cylinder from which the second piston rod projects when the second valve is in a first condition and for connecting the first conduit to said end of the second cylinder from which the second piston rod projects when the second valve is in a second condition, the other end of the second cylinder being permanently connected to said first conduit, so as to enable difierent feed speeds to the turret slide to be obtained by changing the conditions of said first and second valves without altering the speed control devices.

6. In an automatic lathe incorporating a bed, a saddle adjustably mounted on said bed and a cross slide mounted on said saddle for motion in a direction perpendicular to the length of said bed, an hydraulic feed system for driving the cross-slide relative to the saddle, said hydraulic feed system comprising a double-acting cylinder mounted on the saddle, a first piston within said double-acting cylinder, a first piston attached to the first piston and projecting from one end of the double-acting cylinder, a single acting cylinder mounted on the saddle in parallel relationship with the first cylinder, said single acting cylinder being of lesser internal cross-sectional area than double-acting cylinder, 21 second piston slidable in the single acting cylinder, a second piston rod attached to the second piston and projecting from the end of the single-acting cylinder adjacent the end of the doubleacting cylinder from which the first piston rod projects, said piston rods being connected to the cross-slide, a source of pressurised fluid, a reservoir, selectively op erable speed control devices controlling the flow of fluid to the reservoir, first and second conduits connectable to said source and said control devices, said first conduit being permanently connected to the end of the doubleacting cylinder opposite the end thereof from which said first piston rod projects, and said second conduit being permanently connected to the end of said single-acting piston and cylinder unit from which said second piston rod projects, and a valve means which connects said first conduit to the end of the double-acting cylinder from which the first piston rod projects when said valve means is in a first condition and which connects said second conduit to the end of the double-acting cylinder 5 from which the first piston rod projects when said valve means is in a second condition.

7. In an automatic lathe as claimed in claim 6 an adjustable turret rest on the bed, a turret slide movable along the bed, an indexible turret on said turret slide, further hydraulic feed system for moving the turret slide along the bed, said further hydraulic feed system comprising third and fourth identical parallel cylinders attached to the turret rest, third and fourth pistons slidable respectively in said cylinders, third and fourth piston rods secured to the third and fourth pistons respectively and projecting from the cylinders in the same direction, said piston rods being connected to the turret slide, a dummy piston rod on said third piston of cross-sectional area greater than that of the third piston rod and projecting from the end of the third cylinder remote from the end thereof from which the third piston rod projects, a further source of pressurised fluid, further selectively operable speed control devices controlling the flow of fluid to the reservoir, third and fourth conduits connectible to 20 said further source and to said further speed control devices, a first valve for connecting the third conduit to the end of said third cylinder from which the dummy piston rod projects when said first valve is in a first condition third cylinder from which the dummy piston rod projects when said first valve is in a second condition, said fourth conduit being permanently connected to the end of the third piston rod projection, 21 second valve for conmeeting the fourth conduit to the end of the fourth cylinder from which the fourth piston rod projects when the second valve is in a first condition and for connecting the third conduit to the end of the fourth cylinder from which the fourth piston rod projects when the second valve is in a second condition, the other end of the fourth cylinder being permanently connected to the third conduit, and further valve means for connecting both sources of supply to the third conduit to provide sufiicient power for rapid motion of the turret slide during turret indexing with the first valve in said second condition and the second valve in said first condition.

References Cited UNITED STATES PATENTS 1,289,795 12/1918 Johnson 91411 X 1,986,848 1/1935 Perry 8221 X 2,550,148 4/1951 Harding 91-436 X and for connecting the fourth conduit to the end of said 25 DAS VLACH S, Pri ry Examiner. 

5. AN AUTOMATIC LATHE OF THE TYPE DESCRIBED INCLUDING A BED, AN ADJUSTABLE TURRET REST ON THE BED, A TURRET SLIDE MOVABLE ALONG THE BED AND AN HYDRAULIC FEED SYSTEM FOR MOVING THE TURRET SLIDE ALONG THE BED, SAID HYDRAULIC FEED SYSTEM COMPRISING FIRST AND SECOND PARAELLE IDENTICAL CYLINDERS ATTACHED TO THE TURRET REST, FIRST AND SECOND PISTONS SLIDABLE IN SAID CYLINDERS RESPECTIVELY, FIRST AND SECOND PISTON RODS PROJECTING IN THE SAME DIRECTION FROM THE CYLINDERS RESPECTIVELY AND ATTACHED TO THE TURRET SLIDE, A DUMMY PISTON ROD ON SAID FIRST PISTON OF CROSS-SECTIONAL AREA GREATER THAN THAT OF THE FIRST PISTON ROD AND PROJECTING FROM THAT END OF THE FIRST CYLINDER WHICH IS REMOTE FROM THE END THEREOF FROM WHICH SAID FIRST PISTON ROD PROJECTS, A SOURCE OF PRESSURISED FLUID, A RESERVOIR, SELECTIVELY OPERABLE SPEED CONTROL DEVICES CONTROLLING THE FLOW OF FLUID TO THE RESERVOIR, FIRST AND SECOND CONDUITS CONNECTIBLE TO THE SOURCE AND TO SAID SPEED CONTROL DEVICES, SAID FIRST CONDUIT BEING A FIRST VALVE FOR CONNECTING THE FIRST CONDUIT TO THE END OF THE FIRST CYLINDER FROM WHICH THE DUMMY PISTON ROD PROJECTS WHEN SAID FIRST VALVE IS IN A FIRST CONDITION AND FOR CONNECTING SAID SECOND CONDUIT TO THE END OF THE FIRST CYLINDER FROM WHICH THE DUMMY PISTON ROD PROJECTS WHEN THE FIRST VALVE IS IN A SECOND CONDITION, SAID SECOND CONDUIT BEING PERMANENTLY CONNECTED TO THE END OF THE FIRST CYLINDER FROM WHICH THE FIRST PISTON ROD PROJECTS, AND A SECOND VALVE FOR CONNECTING THE SECCOND CONDUIT TO THE END OF THE SECOND CYLINDER FROM WHICH THE SECOND PISTON ROD PROJECTS WHEN THE SECOND VALVE IS IN A FIRST CONDITION AND FOR CONNECTING THE FIRST CONDUIT TO SAID END OF THE SECOND CYLINDER FROM WHICH THE SECOND PISTION ROD PROJECTS WHEN THE SECOND VALVE IS IN A SECOND CONDITION, THE OTHER END OF THE SECOND CYLINDER BEING PERMANENTLY CONNECTED TO SAID FIRST CONDUIT, SO AS TO ENABLE DIFFERENT FEED SPEEDS TO THE TURRET SLIDE TO BE OBTAINED BY CHANGING THE CONDITIONS OF THE FIRST AND SECOND VALVE WITHOUT ALTERING THE SPEED CONTROL DEVICES. 